Is his desk clean?
Is he strong enough to lift a feather duster and whip the vacuum cleaner around?
Having a mountain of tabs open is the equivalent of not putting your tools away, keeping your desk tidy or keeping your house clean.
People that get stuff done tend to be those that keep things tidy. Millions of tabs open might give the impression of 'genius at work', but do the deliverables get delivered?
This might not be a popular opinion, however, after having to tidy up my dad's estate (he never put tools away and his computer had billions of tabs open), I have formed my own conclusions on this.